Multi-zone hydrocaracking process



March 15, 1966 H. F. MASON ETAL MULTI-ZONE HYDROCRACKING PROCESS FiledNov. 26, 1963 ATTORNEYS 3,240,694 MULTI-ZGNE HYDRCRACKING IROEESS HaroldF. Mason, Berkeley, and Ben G. Bray, El Cerrito,

Calif., assianors to Chevron Research Company, a

corporation of Delaware Filed Nov. 26, 1963, Ser. No. 325,943 Claims.(El. 20S-59) This invention relates to a hydrocarbon conversion process,more particularly to a hydrocarbon conversion process for convertingpetroleum distillate and residuum feeds into various valuable products,and still more particularly to a catalytic conversion process capable ofproducing middle distillates and gasoline from said feeds.

It is well known that nitrogen in a hydrocarbon feed is deleterious tocertain hydrocracking catalystis, particularly highly acidichydrocracking catalysts, and that in order to provide a practicalprocess for producing gasoline over a highly acidic hydrocrackingcatalyst from a feed containing substantial amounts of nitrogen, it isgenerally necessary to first hydrofine the feed to remove substantiallyall of the nitrogen. Such highly acidic catalysts do not result in theproduction of substantial quantities of middle distillates, so thatwhere gasoline production and also substantial middle distillateproduction is desired a hydrocracking catalyst having no more than weakacidity is desirable. While it is possible to meet the aforesaidproblems by operating a two-stage process wherein ahydroning-hydrocracking catalyst having no more than weak acidity isused in the first stage and a more acidic hydrocracking catalyst is usedin the second stage, such a process still has undesirable aspects.Operation of the first stage at hydrofining conditions severe enough toreduce the nitrogen content of the feed to an acceptably low levelfrequently results in greater than desired amounts of hydrocracking,catalyst fouling and hydrogen consumption in that stage. On the otherhand, operation of the first stage at less severe conditions which donot result in an excessive amount of hydrocracking frequently leaves agreater concentration `of nitrogen in the effluent from the first stagethan can be tolerated for sustained periods by the acidic catalysts inthe second stage.

In view of the foregoing, it is an object of the present invention toprovide a multi-stage process for converting nitrogen-containing feedsto gasoline and middle distillates wherein said feeds are hydrocrackedand partially hydrofined with hydoiining-hydrocracking catalysts havingno more than weak acidity to produce middle distillate products andhigher boiling materials and wherein selected portions of said higherboiling materials are hydrocracked in a subsequent stage in the presenceof a more acidic catalyst, and wherein it is not necessary to removesubstantially all of the nitrogen from said feeds with said catalystshaving no more than weak acidity in order to produce a feed for saidsubsequent stage having an adequately low nitrogen content.

The invention will best be understood, and further objects andadvantages thereof will be apparent, from the following description whenread in conjunction with the accompanying drawing which is adiagrammatic illustration of process units and flow paths suitable forcarrying out the process of the present invention.

In accordance with one embodiment of the present invention there isprovided a process for producing gasoline and middle distillates from ahydrocarbon feed stock selected from the group consisting ofnitrogen-containing petroleum distillates and petroleum residua boilingabove 350 F., which comprises selecting two feed fractions each havingdifferent boiling ranges, the higher boiling of said fractions boilingabove 560 F., hydrocracking said higher boiling fraction in the presenceof from 1000 to 10,000 s.c.f. of hydrogen per barrel thereof in a nitedStates Patent O first conversion zone at a temperature of from 500 to950 F., a pressure above 500 p.s.i.g., an LHSV of from 0.1 to 4.0, and aper-pass conversion of more than about 40 volume percent of said higherboiling fraction to products boiling below the initial boiling pointthereof, with a hydrofining-hydrocracking catalyst having no more thanweak acidity comprising at least one hydrogenating component selectedfrom the Group VI metals and compounds of Group VI metals and at leastone hydrogenating component selected from the Group VIII metals andcompounds of Group VIII metals in intimate association with asilica-containing support, recovering at least one product boiling below550 F. from said first conversion zone hydroiining the lower `boiling ofsaid fractions with a hydrofining catalyst in a second conversion zoneto reduce the nitrogen content thereof under conditions that accomplishin said second zone a concurrent hydrocracking conversion of less than30 volume percent of the feed thereto to products boiling below theboiling range of said feed, passing to a third conversion zone from saidrst zone a fraction boiling above 550 F. and below the initial yboilingpoint of the feed to said first zone, removing ammonia from thehydrofined fraction from said second conversion zone and passing theresulting hydrofined fraction to said third conversion zone, andhydrocracking in said third conversion zone said fractions passedthereto to produce additional products boiling below 550 F.

In accordance with a more specific embodiment of the present inventionthere is provided a process for producing :gasoline and middledistillates from a hydrocarbon feed stock selected from the groupconsisting of nitrogen-containing petroleum distillates and petroleumresidua boiling above 350 F., containing materials boiling above 560 F.,and also containing materials boiling below 560 F., which comprisesseparating said feed into two feed fractions each having differentboiling ranges, the higher boiling of said fractions boiling .above 560F., hydrocracking said higher boiling fraction in the presence of 1000to 10,000 s.c.f. of hydrogen per barrel thereof in a first conversionzone at a temperature of from 500 to 950 F., a pressure above 500p.s.i.g., an LHSV of from 0.1 to 4.0, and -a per-pass conversion of morethan about l0 volume percent of said higher boiling fraction to productsboiling below the initial boiling point thereof with ahydrofining-hydrocracking catalyst having noi more than weak aciditycomprising at least one hydrogenating component selected from the GroupVI metals and compounds of Group VI metals and at least onehydrogenating component selected from the Group VIII metals andcompounds of Group Vill metals in intimate association with a supportsubstantially less acidic than a conventional silica-aluminahydrocracking support, recovering at least one product boiling below 550F. from said first conversion zone, hydrofining the lower boiling ofsaid fractions by contacting said fraction in a second conversion zonewith a hydrofining catalyst comprising a hydrogenating componentselected from the Group VI metals .and compounds of Group VI metals anda hydrogenating component selected from the Group VIH metals andcompounds of Group VIII metals in intimate association with a supportsubstantially comprising alumina at 500 to 800 F., 500 to 4,000p.s.i.g., an LHSV of 0.2 to l0, and a per-pass conversion of less than30 Volume percent of said lower boiling fraction to products boilingbelow the initial boiling point thereof, in the presence of 500 to10,000 s.c.f. of hydrogen per barrel of sad lower boiling fraction,passing to a third conversion zone from said first zone a fractionboiling above 550 F. and below the initial boiling point of the feed tosaid first zone, removing ammonia from the hydrofined fraction from saidsecond conversion zone and passing the resulting hydrofined fraction tosaid third conversion zone and hydrocracking in said third conversionzone said fractions passed thereto to produce additional productsboiling below 550 F.

Suitable feeds for use in the process of the present invention includenitrogen-containing petroleum distillates and nitrogen-containingpetroleum residua and mix- -tures thereof, from which a higher boilingfraction, boiling above 560 F., and a lower boiling fraction can beselected. Heavy gas oils and catalytic cycle oils are excellent feeds tothe process, as well as conventional FCC feeds and portions thereof.Residual feeds may include Minas and other parafiinic-type residua.

The aforesaid hydrofining catalyst comprises at least one hydrogenatingcomponent selected from the Group VI metals and compounds of Group VImetals and at least one hydrogenating component selected from the GroupVIII metals and compounds of Group VIII metals. Preferred combinationsof hydrogenating components include nickel sulfide and tungsten sulfide,nickel sulfide and molybdenum sulfide, land palladium sulfide andmolybdenum sulfide.

The aforesaid hydrofining catalyst comprises a support, preferably onethat is not more than moderately acidic, as compared with highly acidicsupports such as silica-alumina. Said support preferiably is alumina.

The aforesaid hydrofining-hydrocracking catalyst having no more thanweak acidity comprises at least one hydrogenating component selectedfrom the Group VI metals and compounds of Group VI metals rand at leastone hydrogenating component selected from the Group VIII metals andcompounds of the Group VIII metals. Preferred combinations ofhydrogenating components include nickel sulfide and tungsten sulfide,nickel sulfide and molybdenum sulfide, and palladium sulfide andmolybdenum sulfide.

The aforesaid hydrofining-hydrocnacking catalyst having no more thanweak acidity comprises a support, preferably one that is moderatelyacidic, but not more than moderately acidic, as compared with highlyacidic supports such as silica-alumina. Said support preferably isselected from the group consisting of silica-magnesia supports,silica-alumina supports containing less than 70 weight percent ofsilica, and silica-alumina-magnesia supports having :a silica contentless than 80 weight percent.

rPhe aforesaid hydrofining-hydrocracking catalyst having no more thanweak acidity is relatively nitrogeninsensitive compared withconventional acidic hydrocracking catalysts such as nickel sulfide onsilica-alumina. Accordingly, the nitrogen content of thenitrogen-containing feed used in the process of the present inventionmay be relatively high and excellent hydrocracking results still may beobtained in lthe conversion zones containing said catalysts atreasonable temperatures without the necessity for rapidly raising thetemperature yto maintain conversion as is necessary when hydrocracking ahigh nitrogen content feed of a conventional acidic hydrocrackingcatalyst, such as nickel sulfide on silicaalumina. The nitrogen contentof the feed in the present process may range from l parts per million to7000 parts per million or more. The process is especially attractive forprocessing heavy feeds containing at least 500 parts per millionnitrogen.

Although high nitrogen content feeds can be tolerated by saidhydrofining-hydrocracking catalysts having no more than weak acidity, itwill be noted that said catalysts also are excellent hydrodenitricationcatalysts and are eicient in concurrently hydrofining as well as inhydrocnacking the feed. Nevertheless, the process of the presentinvention may be rendered even more efficient if very high nitrogencontent feeds are first hydrofined by conventional methods t0 at leastsomewhat reduce their nitrogen content before hydrocracking them in thepresence of said catalysts having no more than weak acidity inaccordance with the present invention.

The conversion zone in the process of the present invention containingsaid hydrofining-hydrocracking catalyst having no more than weak acidityis operated at combinations of conditions selected from within thefollowing ranges that will produce the desired degree of hydrocracking;a temperature of about 500 to 950 F., preferably 650 to 850 F.; ahydrogen partial pressure of 500 to 3500 p.s.i.a., preferably 1000 to2500 p.s.i.a.; an LHSV of from about 0.1 to 4.0, preferably 0.4 to 2.0;and a per-pass conversion above about 40 percent. The hydrogen flow tosaid conversion zone may be from 1000 to 10,000 s.c.f. per barrel offeed, and preferably 2500 to 8000 s.c.f. per barrel of feed. The higherhydrogen partial pressures, particularly with unrefined feeds, givelower catalyst fouling rates, and therefore, for longer catalyst lives,it is preferable to operate above 2000 p.s.i.g. total pressure and above1000 p.s.i.g. hydrogen partial pressure.

The catalyst in the conversion zone subsequent to the hydrofiningconversion zone and the hydrofining-hydrocracking conversion zone may beany conventional active acidic hydrocracking catalyst, for examplenickel sulfide on silica-alumina, platinum on silica-alumina, cobaltsulfide on silica-alumina, various conventional fluorided acidichydrocracking catalysts, etc.

Said subsequent conversion zone may be operated under conventionalhydrocracking conditions, for example a total pressure of from 500 to3000 p.s.i.g., a hydrogen partial pressure of at least 350 p.s.i.g., atemperature of from 550 to 850 F., an LHSV of from about 0.1 to 4.0, anda per-pass conversion above about 40 percent. Generally, at least 300s.c.f. of hydrogen per barrel of feed vwill be supplied to saidsubsequent conversion zone, wherein normally from about 1000 to 2000s.c.f. of hydrogen are consumed in the hydrocracking reaction per barrelof feed converted to synthetic products.

It is well known that nitrogen has an extremely deleterious effect uponthe hydrocracking performance of acidic hydrocracking catalysts such asthose used in said subsequent zone in the present process. It is wellknown that as the nitrogen content of the feed to a hydrocracking zonecontaining an acidic hydrocracking catalyst increases, the reactiontemperature must be raised if desired conversion levels are to bemaintained. It is also well known that if the temperature must be raisedbeyond a certain point, for example 850 F., side reactions andnonhydrocracking reactions occur to an intolerable extent. Accordingly,it is well known that the nitrogen content of the feed to ahydrocracking zone containing an acidic hydrocracking catalyst should bekept below about 50 parts per million, preferably below about 10 partsper million, and still more preferably below about 2 parts per million.Therefore, in a multi-stage process of the type with which the presentinvention is concerned, namely one in which a hydrofining-hydrocrackingcatalyst of not more than weak acidity, for example of moderate acidity,is used in a first stage and a highly acidic hydrocracking catalyst isused in a subsequent stage, the first stage heretofore has been operatedat severe enough hydrofining conditions to reduce the nitrogen contentof the total hydrofined feed to a level low enough for passing to thesubsequent stage. Frequently, such severe conditions in the first stagehave resulted in an undesirably high level of hydrocracking in thatstage. Heretofore, the operator of such a process faced a dilemma; ifthe first stage were operated at sufficiently mild hydrocrackrngconditions, insufficient hydrofining would be accomplished to reduce thenitrogen content of the feed to the subsequent stage to a tolerably lowlevel.

Heretofore, it has been thought that the nitrogen concentration in theefliuent from the first stage of the aforesaid type of process has beendistributed relatively uniformly through said effluent, and that if saideffluent were fractionated, nitrogen would appear in the variousfractions in approximately the same concentration. Very unexpectedly, ithas now been discovered that this is not so, but rather that thenitrogen concentration in the synthetic portion of the effluent, namelythat portion boiling below the initial boiling point of the feed, isvery substantially lower than the nitrogen concentration in that portionof the efiluent boiling within the feed boiling range. This surprisingdiscovery has far-reaching consequences in the operation of amulti-stage process of the aforesaid type. In accordance with thepresent invention, it is now possible t-o operate a first stage,containing a hydrofining-hydrocracking catalyst having no more than weakacidity, at adequately mild hydrocracking conditions and permit theefiiuent from said stage to contain a much higher total nitrogen contentthan was heretofore possible. This is accomplished by processing in thesubsequent stage containing a highly acidic caatlyst only thosematerials in the efliuent from said first stage that boil below theinitial boiling point of the feed to that first stage. These materials,termed synthetic materials because they do not contain any materialsboiling within the boiling range of the original feed to the stage inwhich they are produced, contain a very low concentration of nitrogendespite the fact that the higher boiling materials have a substantiallyhigher nitrogen concentration. This rnay be illustrated by the followingexamples:

Example 1 A 70 to 900 F. boiling range petroleum distillate containing2450 parts per million nitrogen was hydrocracked over a nickel-tungstenon silica-magnesia catalyst under conditions within the aforesaid firstconversion zone ranges. The whole hydrocracked product contained 50parts per million nitrogen; however, it was found that only 2 parts permillion `of the said 50 parts per million nitrogen appeared in the 550to 700 F. synthetic portion of the hydrocrackate.

Exam pla 2 A hydrocarbon feed boiling between 550 and 1000 F., andcontaining 4050 p.p.rn. total nitrogen is separated into two portions,boiling above and below about 775 F., respectively.

The heavier of the aforesaid feed portions, containing 5650 ppm. totalnitrogen, is hydrofined-hydrocracked in a first conversion zone in thepresence of a catalyst comprising nickel sulfide, tungsten sulfide andSilica-magnesia at a temperature `of 750 F. and a pressure of 2000p.s.i.g., at a per-pass conversion of 50 liquid volume percent of saidfeed to materials boiling below the initial boiling point of ysaid feed.From the effluent from said zone materials boiling above about 700 F.are recycled to said zone. The t-otal nitrogen content of the SOO-700 F.portion of said effluent is 0.12 p.p.m.

The lighter of the aforesaid feed portions, containing 2450 ppm. totalnitrogen, is hydrofined on a oncethrough basis in a second conversionzone in the presence of a catalyst comprising nickel sulfide, tungstensulfide and silica-magnesia at a temperature of 750 F. The effluent fromsaid second conversion zone boils from 550 to 800 F. and has a totalnitrogen content of 0.14 p.p.m.

The efliuent from said second conversion zone is blended with said500-700 F. portion of the efliuent from said first conversion zone. Theresulting blended product has a total nitrogen content of 0.13 p.p.m.

Example 3 For comparison purposes, the same feedstock used in Example 2instead of being separated into two portions as in Example 1 is passedwithout separation into Contact in a conversion zone with the samecatalyst used in both conversion zones in Example 2, on a once-throughbasis at a .temperature of 750 F. and a pressure of 2000 p.s.i.g. Theeffluent from said conversion Zone boils from 550 to 1000 F. and has atotal nitrogen content of 6.3 ppm.

fi In order to obtain a nitrogen content of 0.13 ppm., as is obtained inthe operation in Example 2, the temperature for the operation in thisExample 3 would have to be raised 20 F., which would cause a substantialincrease in catalyst fouling rate.

Example 4 Referring now to the drawing, there shown is an exemplarydiagrammatic illustration of an embodiment of process units and flowpaths suitable for carrying out the process of the present invention.

A hydrocarbon feed which may be, and in this example is, a petroleumdistillate feed boiling above 350 F. and containing materials boilingabove 560 F. is passed through line 1 to distillation column 2 where itis separated into various fractions as shown. A gaseous fraction may beremoved from column 2 through line 3, and a residum fraction boilingabove 1100 F. may be removed through line 4, if desired. Fraction A,having an initial boiling point above 560 F., is passed fromdistillation column 2 through line 5 to hydrofining-hydrocracking zone6. Fraction B, boiling from approximately the initial boiling point ofthe feed in line 1 to the initial boiling point of fraction A, is passedfrom distillaton column 2 through line 7 to hydrolining Zone 8.

Fraction A is hydrofined and hydrocracked in zone 6 with the aforesaidhydrofining-hydrocracking catalyst having no more than weak acidity andwith hydrogen entering zone 6 through line 9 under the hydrocrackingconditions previously discussed, including a per-pass conversion aboveabout 40 volume percent of fraction A to products boiling below theinitial boiling point of frac- Ation A. From zone 6, an effluent ispassed through line 10 to separation zone 15 from which hydrogen isrecycled through line 16, ammonia is withdrawn through line 17, andremaining materials are passed through line 18 to separation zone 19.From separation Zone 19 a product stream boiling below about 550 F., forexample including gasoline and jet fuel components, is withdrawn throughline 20. From separation zone 19, materials boiling above the initialboiling point of fraction A, i.e., materials boiling within the range ofthe feed entering zone 6 through line 5, are returned to zone 6 throughline 25. From separation zone 19 a fraction boiling from about 550 F. tothe initial boiling point of fraction A, i.e., approximately above thejet fuel boiling range and below the initial boiling point of the feedto zone 6, is passed through line 26 into contact in hydrocracking Zone27 with the aforesaid highly acidic hydrocracking catalyst and withhydrogen entering zone 27 through line 28 under the hydrocrackingconditions previously discussed, including a per-pass conversion aboveabout 40 percent.

Fraction B is contacted in hydrofining Zone 8 with the aforesaidhydrofining catalyst and with hydrogen enternig zone 8 through line 29under the hydroiining conditions previously discussed, including aper-pass conversion of less than about 30 volume percent of fraction Bto products boiling below the initial boiling point of fraction B. Fromzone 8 an efiiuent is passed through line 30 to separation zone 35 fromwhich hydrogen is recycled through line 36 to zone 8, ammonia iswithdrawn through line 37, and remaining materials are passed throughline 38 into contact in hydrocracking zone 27 with the aforesaid highlyacidic hydrocracking catalyst and with hydrogen entering zone 27 throughline 28, under the hydrocracking conditions previously discussed,including a per-pass conversion of above about 40 percent of saidremaining materials to products boiling below the initial boiling pointof said remaining materials. The hydrocrackate effluent from zone 27 ispassed through line 39 to separation zone 40 for separation intoproducts boiling below about 550 F., which are passed through line 45,and materials boiling above about 550 F. which are returned to zone 40through line 46 for further proessing.

The nitrogen concentration in the stream passed through line 26 toconversion zone 27 is lower than the nitrogen concentration in thestream returned through line 25 to conversion zone 6, and accordingly agiven volume of the stream in line 26 will be less deleterious to thehydrocracking catalyst in zone 27 from the standpoint of nitrogenpoisoning than the same Volume of the stream in line 25, even though thetotal nitrogen concentration of the stream in line 18 may be higher thanpermissible for a suitable feed stock to zone 27.

From the foregoing, it will be seen that the process of the presentinvention is effective in producing both middle distillates, inparticular jet fuels, and gasoline in varying ratios from heavy,nitrogen-containing feed stocks. It will also be seen that the processembodies a discovery which permits the production in the zone containingthe hydrofining-hydrocracking catalyst having no more than weak acidityunder surprisingly mild hydrofining conditions of fractions, havingadequately low nitrogen contents to be suitable feed stocks for thesubsequent conversion zone containing a catalyst having a high acidity.

Although only specific embodiments of the present invention have beendescribed, numerous variations can be made of those embodiments withoutdeparting from the spirit of the invention, and all such variations thatfall within the scope of the appended claims are intended to be embracedthereby.

We claim:

1. A process for producing gasoline and middle distillates from ahydrocarbon feed stock selected from the group consisting ofnitrogen-containing petroleum distillates and petroleum residua boilingabove .350 F., which comprises selecting two feed fractions each havingdifferent boiling ranges, the higher boiling of said fractions boilingabove 560 F., hydrocracking said higher boiling fraction in the presenceof from 1000 to 10,000 s.c.f. of hydrogen per barrel thereof in a firstconversion zone at a temperature of from 500 to 950 F., a pressure above500 p.s.i.g., an LHSV of from 0.1 to 4.0, and a per-pass conversion ofmore than about 40 volume percent of said higher boiling fraction toproducts boiling below the initial boiling point thereof, with ahydrofining-hydrocracking catalyst having no more than weak aciditycomprising at least one hydrogenating component selected from the GroupVI metals and compounds of Group VI metals and at least onehydrogenating component selected from the Group VIII metals andcompounds of Group VIII metals in intimate association with asilica-containing support, recovering at least one product boiling below550 F. from said first conversion zone, hydrofining the lower boiling ofsaid fractions with a hydrofining catalyst in a second conversion zoneto reduce the nitrogen content thereof under conditions that accomplishin said second zone a concurrent hydrocracking conversion of less than30 volume percent of the feed thereto -to products boiling below theboiling range of said feed, passing to a third conversion zone from saidfirst zone a fraction boiling above 550 F. and below the initial boilingpoint of the feed to said first zone, removing ammonia from thehydrofined fraction from said Isecond conversion zone and passing theresulting hydrofined fraction to said third conversion zone, andhydrocracking in said third conversion zone said fractions passedthereto to produce additional products boiling below 550 F.

2. A process as in claim 1, wherein said third conversion zone containsa hydrocracking catalyst comprising at least one hydrogenating componentin intimate association with an active, acid support, and wherein saidthird conversion Zone is operated at a temperature of from 550 to 900F., a pressure above 500 p.s.i.g., and an LHSV of 0.1 to 4.0.

3. A process as in claim 1, wherein a fraction boiling within the rangeof the feed to said first conversion zone is recycled to said firstconversion zone from the effluent thereof.

4. A process as in claim 1, wherein a fraction boiling within theboiling range of said fractions passed to said third conversion zone isrecycled to said third conversion zone from the effluent thereof.

5. A process for producing gasoline and middle distillates from ahydrocarbon feed stock selected from the group consisting ofnitrogen-containing petroleum distillates and petroleum residua boilingabove 350 F., con taining materials boiling above 560 F., and alsocontaining materials boiling below 560 F., which comprises separatingsaid feed into two feed fractions each having different boiling ranges,the higher boiling of said fractions boiling above 560 F., hydrocrackingsaid higher boiling fraction in the presence of 1000 to 10,000 s.c.f. ofhydrogen per barrel thereof in a first conversion zone at a temperatureof from 500 to 950 F., a pressure above 500 p.s.i.g., an LHSV of fromOrl to 4.0, and a per-pass conversion of more than about 40 volumepercent of said higher -boiling fraction to products boiling below theinitial boiling point thereof with a hydrofining-hydrocracking catalysthaving no more than weak acidity comprising at least one hydrogenatingcomponent selected from the Group VI .metals and compounds `of Group VImetals and at least one hydrogenating component selected from the GroupVIII metals and compounds of Group VIII metals in intimate associationwith a support substantially less acidic than a conventionalsilica-alumina hydrocracking support, recovering at least one productboiling below 550 F. from said first conversion zone, hydrofining thelower boiling of said fractions by contacting said fraction in a secondconversion zone with a hydrolining catalyst comprising a hydrogenatingcomponent selected from the Group VI metals and compounds of Group VImetals and a hydrogenating component selected from the Group VIIImetal-s and compounds of Group VIII metals in intimate association witha support substantially comprising alumina at 500 to 800 F., 500 to4,000 p.s.i.g., an LHSV of 0.2 to 10, and a per-pass conversion of lessthan 30 volume percent of said lower boiling rfraction to productsboiling below the initial boiling point thereof, in the presence of 500to 10,000 s.c.f. of hydrogen per barrel of said lower boiling fraction,passing to a third conversion zone from said first zone a fractionboiling above 550 F. and below the initial boiling point of the feed tosaid rst zone, removing ammonia from the hydroned fraction from saidsecond conversion zone and passing the resulting hydroiined fraction tosaid third conversion zone and hydrocracking in said third conversionzone said fractions passed thereto to produce additional productsboiling below 550 F.

References Cited by the Examiner UNITED STATES PATENTS 3,026,260 3/1962Watkins 208-59 3,159,568 12/1964 Price et al 208-111 3,175,966 3/1965Burch 208-79 DELBERT E. GANTZ, Primary Examiner.

1. A PROCESS FOR PRODUCING GASOLINE AND MIDDLE DISTILLATES FROM AHYDROCARBON FEED STOCK SELECTED FROM THE GROUP CONSISTING OFNITROGEN-CONTAINING PETROLEUM DISTILLATES AND PETROLEUM RESIDUA BOILINGABOVE 350*F., WHICH COMPRISES SELECTING TWO FEED FRACTIONS EACH HAVINGDIFFERENT BOILING RANGES, THE HIGHER BOILING OF SAID FRACTIONS BOILINGABOUT 560*F., HYDROCRACKING SAID HIGHER BOILING FRACTION IN THE PRESENCEOF FROM 1000 TO 10,000 S.C.F. OF HYDROGEN PER BARREL THEREOF IN A FIRSTCONVERSION ZONE AT A TEMPERATURE OF FROM 500*F., A PRESSURE ABOVE 500P.S.I.G., AN LHSV OF FROM 0.1 TO 4.0, AND A PER-PASS CONVERSION OF MORETHAN ABOUT 40 VOLUME PERCENT OF SAID HIGHER BOILING FRACTION TO PRODUCTSBOILING BELOW THE INITIAL BOILING POINT THEREOF, WITH AHYDROFINING-HYDROCRACKING CATALYST HAVING NO MORE THAN WEAK ACIDITYCOMPRISING AT LEAST ONE HYDROGENATING COMPONENT SELECTED FROM THE GROUPVI METALS AND COMPONENTS OF GROUP VI METALS AND AT LEAST ONEHYDROGENATING COMPONENT SELECTED FROM THE GROUP VII METALS AND COMPOUNDSOF GROUP VII METALS IN INTIMATE ASSOCIATION WITH A SILICA-CONTAININGSUPPORT, RECOVERING AT LEAST ONE PRODUCT BOILING BELOW 550*F. FROM SAIDFIRST CONVERSION ZONE, HYDROFINING THE LOWER BOILING OF SAID FRACTIONSWITH A HYDROFINING CATALYST IN A SECOND CONVERSION ZONE TO REDUCE THENITROGEN CONTENT THEREOF UNDER CONDITIONS THAT ACCOMPLISH IN SAID SECONDZONE A CONCURRENT HYDROCRACKING CONVERSION OF LESS THAN 30 VOLUMEPERCENT OF THE FEED THERETO TO PRODUCTS BOILING BELOW THE BOILING RANGEOF SAID FEED, PASSING TO A THIRD CONVERSION ZONE FROM SAID FIRST ZONE AFRACTION BOILING ABOVE 550*F. AND BELOW THE INITIAL BOILING POINT OF THEFEED TO SAID FIRST ZONE, REMOVING AMMONIA FROM THE HYDROFINED FRACTIONFROM SAID SECOND CONVERSION ZONE AND PASSING THE RESULTING HYDROFINEDFRACTION TO SAID THIRD CONVERSION ZONE, AND HYDROCRACKING IN SAID THIRDCONVERSION ZONE SAID FRACTIONS PASSED THEREBY TO PRODUCE ADDITIONALPRODUCTS BOILING BELOW 550*F.